GFSK modulation is widely used in transmitters such as digital enhanced cordless telecommunication transmitters. A conventional GFSK modulator is based on an open-loop phase lock loop (PLL). However, open-loop PLLs usually have a frequency shift which can cause an increase in residual frequency modulation and worsen stability of a receiving system.
Accordingly, a GFSK modulator which is capable of controlling residual frequency modulation and ensuring stability of the receiving system is desirable.